    window.onload = function() {
      var imgList = [],liList = [],headList = [],contentList = [],skillImgList = [],deviceImgList = [],experienceImgList = [];
      var imgSrc = $('.events-img img');
      var liSrc = $('.events-list li');
      var headSrc = $('.head-mask p');
      var contentSrc = $('.content-mask div');
      var skillImgSrc = $('#photo-skill-img img');
      var skillLiSrc = $('#photo-skill li');
      var deviceImgSrc = $('#device-img img')
      var deviceSrc = $('#device li');
      var experienceImgSrc = $('#experience-img img');
      var experienceSrc = $('#experience li');
      // events change
      for(var i=0;i<liSrc.length;i++) {
        imgList.push(imgSrc[i]);
        liList.push(liSrc[i]);
        headList.push(headSrc[i]);
        contentList.push(contentSrc[i]);
      }
      var j=0;
      $('.events-list li').on('mouseover',function(event) {
        for(i=0;i<liList.length;i++){
          if(liList[i] == this){
            for(j=0;j<imgList.length;j++){
              imgList[j].style.zIndex = 0;
              headSrc[j].style.display = 'none';
              contentSrc[j].style.display = 'none';
            }
            imgList[i].style.zIndex = 1;
            headSrc[i].style.display = 'block';
            contentSrc[i].style.display = 'block';
            break;
          }
        }
      });
      // skill change
      for(i=0;i<skillImgSrc.length;i++) {
        skillImgList.push(skillImgSrc[i]);
        // console.log(skillImgSrc[i]);
      }
      $('.skill-items li').on('mouseover',function() {
        for(i=0;i<skillImgList.length;i++) {
            if(skillLiSrc[i] === this) {
                for(j=0;j<skillImgList.length;j++){
                    skillImgList[j].style.zIndex = 0;
                }
                skillImgList[i].style.zIndex = 1;
            }
        }
      });
      // device change
      for(i=0;i<deviceImgSrc.length;i++) {
        deviceImgList.push(deviceImgSrc[i]);
        // console.log(deviceImgSrc[i]);
      }
      $('#device li').on('mouseover',function() {
        for(i=0;i<deviceImgList.length;i++) {
            if(deviceSrc[i] === this) {
                for(j=0;j<deviceImgList.length;j++){
                    deviceImgList[j].style.zIndex = 0;
                }
                deviceImgList[i].style.zIndex = 1;
            }
        }
      });
      // experience change
      for(i=0;i<experienceImgSrc.length;i++) {
        experienceImgList.push(experienceImgSrc[i]);
      }
      console.log(experienceImgSrc);
      $('#experience li').on('mouseover',function() {
        for(i=0;i<experienceImgList.length;i++) {
            if(experienceSrc[i] === this) {
                for(j=0;j<experienceImgList.length;j++){
                    experienceImgList[j].style.zIndex = 0;
                }
                experienceImgList[i].style.zIndex = 1;
            }
        }
      });
    }